James Cameron was in Beverly Hills offering his seemingly hypocritical opinion on Hollywood’s 3-D retro-fitting practices again yesterday. Speaking at the Blu-ray industry event Blu-Con, he re-stated how the studios are wrong to think they can convert a movie into 3-D during the normal post-production time frame and so they end up with disappointing visuals a la “Clash of the Titans.” This time around, though, he could (as he did to the NY Times a few weeks ago) bring up the recent situation with “Harry Potter and the Deathly Hallows, Part 1” (like “Clash,” a Warner Bros. title), which appears to support his case in a different way:

“The same studio making the same mistake,” he pointed out, as quoted by BBC News. “Except really getting spanked for it now because they didn’t get the film done. They announced it in 3-D – threw a bunch of money trying to convert it to 3-D in post-production and it simply didn’t work. They just didn’t get it done.”

Of course, Cameron is okay with the 3-D retro-fitting of his own “Titanic,” due out rather tastelessly on the disaster’s centennial in 2012, and maybe “Terminator 2,” because there will be more time to do these correctly. By his logic, then, it would be much more acceptable for Warner Bros. to re-release “Harry Potter and the Sorcerer’s Stone” in 3-D. So long as they spent an adequate amount of years and dollars on it.

“Unless you have a time machine to go back and shoot it in 3-D, you have no other choice,” the “Avatar” director claimed. “The best alternative is if you want to release a movie in 3-D – make it in 3-D.”

Or release it in 2-D and then wait a while to re-release it in 3-D, apparently. Or invent a time machine — and don’t think you’d be surprised if Cameron was the one who got that accomplished. Well, he’d probably only develop some kind of camera that can film the past rather than bring someone back. For now, he’s interested in the sort of time traveling that would bring cinema of the past into the future via new technologies.

“My personal philosophy is that post conversion should be used for one thing and one thing only – which is to take library titles that are favorites that are proven, and convert them into 3-D – whether it’s “Jaws” or “ET” or “Indiana Jones,” “Close Encounters”… or “Titanic.””

With almost $1 billion grossed worldwide, “Sorcerer’s Stone” is certainly a “proven” title, and perhaps that means Warner Bros. should be looking to its cash-cow franchise as a whole and bringing it back step by step, in full, once the second part of “Deathly Hallows” has hit theaters and the series has been exhausted of original possibilities. Similar to what George Lucas is doing with the “Star Wars” movies. I mean, I’m not condoning this anymore than I would encourage Turner’s “Colorized Classics” had I been blogging at the time of that controversial process’ introduction. If I was into giving business advice, though…